Portable electronic devices are used in a multitude of ambient light conditions, which can significantly affect a user's perception of the displayed content on such devices. The human vision system has some ability to adapt to these different ambient lighting conditions. However, even with these adaptive abilities, in different ambient light conditions a user will perceive the display differently, and in some ambient light conditions the user's perception of the display will be degraded. For example, in bright ambient light a dim display may be hard to see.
One mobile phone device that attempts to address this issue uses an ambient light detector to measure a current brightness level of the ambient light. The mobile phone then bins the current brightness level into one of a plurality of brightness ranges, and adjusts a backlight brightness value for the display based on the ambient brightness range in which the detected current ambient brightness level falls. This prior approach has the advantages of improving the display visibility based on the detected current brightness of the ambient light, and saving battery power when a fully bright display is not required.
However, one drawback of such devices is that since the display brightness is adjusted based on a current ambient brightness level, when a user travels from a bright environment to a dark one, or vice versa, the display may be either too bright or too dim for the user, because the user's eyes have not yet adjusted to the new ambient light environment. Another drawback is that the user's perception of the color of the display may be degraded by the color of ambient light. For example, a user viewing a display in tungsten light may perceive a display's colors to be shifted toward a blue region of the color spectrum as compared to when viewing the same display in daylight. Similarly, a user viewing a display in the light of early morning or late evening, which has a different color profile than midday light, may perceive the colors of the display as altered as compared to midday.
According to another prior approach, a geographic location is entered into a software program on a computing device, along with a type of night time light source. The software program calculates a preset twenty four hour color shift curve. The software program then proceeds to shift the color of the display according to the preset twenty four hour color shift curve throughout the day and night. While such an approach attempts to adjust the display to a color that is closer to the daylight or night time light source by which the user views the device, the approach nonetheless suffers from the drawback that the color shifting curve is preset and as a result differences between the actual ambient light conditions and the display as modified by the color shifting curve often and inevitably result. These differences can cause the display to appear to be too red or too yellow, for example, resulting in a sub-optimal display viewing experience.
As a result of these wide variances in user perception of displayed images in different ambient light conditions, the user's experience with the portable electronic device may be degraded, potentially frustrating both the user, and the sales of the portable electronic device.